This invention relates to the shaping of heat-softened glass sheets or the like by pressing the sheets between two solid shaping members of complementary curvature, namely, a male shaping member of convex configuration and a female shaping member of concave configuration. This technique, known as press bending, lends itself to relatively inexpensive mass production of bent glass sheets within precise tolerances. More particularly, the invention relates to press bending glass sheets so as to produce bends of very sharp curvature known as "V" bends, wherein the female shaping member of concave configuration comprises two or more segments hinged together to rotate about an axis approximately coextensive with the line of sharp bending in the glass. While such a hinged shaping member avoids stretching the heat-softened glass sheets when making "V" bends, it is sometimes found nevertheless that the quality of the glass is impaired by scuffing of the soft glass surfaces caused by a slight slippage of the glass sheet relative to the shaping surfaces as the shape of the glass is transformed from planar to curved. This problem is usually encountered when making bends having a radius of curvature along one edge substantially different from the radius of curvature along the opposite edge.
Press bending in general is a well known technique for shaping glass sheets, a particularly advantageous example of which may be seen in U.S. Pat. No. 3,367,764 to S. L. Seymour. Hinged shaping members were also known in the prior art, such as those disclosed in U.S. Pat. No. 3,251,672 to Touvay et al.; U.S. Pat. No. 3,682,613 to Johnson et al.; and Belgian Pat. No. 575,806 to St. Gobain. Each of these prior art hinged presses, however, is hinged so as to place the axis of rotation parallel to and essentially contiguous with the overlying portion of the glass sheet being bent.
In another type of prior art process for bending glass sheets known as gravity sag bending, wherein glass sheets are supported on shaped outline rings as the glass is heated and sags by the force of gravity, it is known to use outline rings which have counterweighted sections that pivot upwardly as the glass sags. When fabricating such pivoted outline rings for the gravity sag bending process, it has been the practice to vary the locations of the pivot points for the counterweighted sections through a relatively wide range of locations in order to achieve the desired arc for the upward swinging motion. However, such a practice did not provide a teaching for how to reduce scuff mark defects when press bending glass sheets to form "V" bends.